What sort of signal do navigation satellites emit? Why can’t I receive them when I am inside? I can get radio signals.

• What sort of signal do navigation satellites emit? Why can’t I receive them when I am inside? I can get radio signals.

At a guess, radio towers are hooked up to mains power and are a lot closer to you…

pesce.del.giorno said:

What sort of signal do navigation satellites emit? Why can’t I receive them when I am inside? I can get radio signals.

UHF.

Materials interfere with the signal and indoors there are other sources of interference.

Also, presumably, when indoors, you know where you’re going…

> Why can’t I receive them when I am inside?

You should be able to get satnav signals inside, unless the walls or roof of your house are made of steel or reinforced concrete.

“In the case of the original GPS design, two frequencies are utilized; one at 1575.42 MHz (10.23 MHz × 154) called L1; and a second at 1227.60 MHz (10.23 MHz × 120), called L2. “

Compare that with microwave, 300 MHz to 300 GHz, and UHF 300 MHz to 3 GHz. UHF TV channels in Australia don’t use higher than 800 MHz. For other UHF applications in the same frequency range as satnav see: https://upload.wikimedia.org/wikipedia/commons/4/45/United_States_Frequency_Allocations_Chart_2003_-_The_Radio_Spectrum.jpg

Moll, GPS units usually fail to get signal inside a building. The waves simply do not penetrate solids. You don’t have to be inside. Standing next to a tall building or under heavy rainforest canopy can also cause them to lose the signal. I believe that part of it is also to do with the type of aerial used.

The old Garmin etrex H series would lose signal on a cloudy day. I’m currently using a Rino650. This is the best handheld I’ve ever used in terms of holding a signal and even this unit will lose signal in really heavy rainforest.

There’s a quick explanation here

Teleost said:

Moll, GPS units usually fail to get signal inside a building. The waves simply do not penetrate solids. You don’t have to be inside. Standing next to a tall building or under heavy rainforest canopy can also cause them to lose the signal. I believe that part of it is also to do with the type of aerial used.

The old Garmin etrex H series would lose signal on a cloudy day. I’m currently using a Rino650. This is the best handheld I’ve ever used in terms of holding a signal and even this unit will lose signal in really heavy rainforest.

There’s a quick explanation here

That link is broken.

All I can comment further is that the higher the frequency the more sensitive signals are to rain, and I suppose the water content of a rainforest could cause problems as well. But these frequencies shouldn’t be high enough to run into that sort of problem.

Teleost said:

Moll, GPS units usually fail to get signal inside a building. The waves simply do not penetrate solids. You don’t have to be inside. Standing next to a tall building or under heavy rainforest canopy can also cause them to lose the signal. I believe that part of it is also to do with the type of aerial used.

The old Garmin etrex H series would lose signal on a cloudy day. I’m currently using a Rino650. This is the best handheld I’ve ever used in terms of holding a signal and even this unit will lose signal in really heavy rainforest.

There’s a quick explanation here

Hold on, found the link now. “The signals sent from these satellites do not penetrate all kinds of barriers with ease. When you use a GPS inside a building, a wide variety of physical barriers and potential interference sources make it difficult for the device to pinpoint your location accurately.”

That’s not a valid explanation. I think it’s more a case of GPS signals being so weak that any sort of interference will stuff them up.

mollwollfumble said:

Teleost said:

Moll, GPS units usually fail to get signal inside a building. The waves simply do not penetrate solids. You don’t have to be inside. Standing next to a tall building or under heavy rainforest canopy can also cause them to lose the signal. I believe that part of it is also to do with the type of aerial used.

The old Garmin etrex H series would lose signal on a cloudy day. I’m currently using a Rino650. This is the best handheld I’ve ever used in terms of holding a signal and even this unit will lose signal in really heavy rainforest.

There’s a quick explanation here

Hold on, found the link now. “The signals sent from these satellites do not penetrate all kinds of barriers with ease. When you use a GPS inside a building, a wide variety of physical barriers and potential interference sources make it difficult for the device to pinpoint your location accurately.”

That’s not a valid explanation. I think it’s more a case of GPS signals being so weak that any sort of interference will stuff them up.

This:

I think it’s more a case of GPS signals being so weak that any sort of interference will stuff them up.

>>holding a signal and even this unit will lose signal in really heavy rainforest.

Yep, last time I tried to use one in dense forest up in the McPherson ranges was about 6 years ago with a good Magellan one but no go, back to map and compass.